Unique physical properties and an abundant supply have established asphalt as a major raw material for use in industrial applications that involve structural adhesive and waterproof protective films. The major markets for these industrial applications are road paving and roofing respectively. Although these two markets have final products that are physically quite different, certain basic similarities do exist. For instance, both asphalt cement and mineral filled roofing asphalt can consist of the combination of asphalt with silica or limestone based minerals. Consequently, chemical and physical factors which can influence the asphaltic coating of minerals are operative in both applications.
Residual oils and/or bituminous materials, such as asphalt, used in the preparation of pavements do not coat and adhere well to mineral aggregates unless the aggregate is substantially dry, and, for this reason, in conventional pavements it may be necessary to dry the mineral aggregate prior to blending with the bituminous material.
Mineral aggregates employed in road pavement range in character from hydrophilic to hydrophobic. In general, siliceous and acidic minerals, such as sands and gravels, tend to be hydrophilic while calcareous, alkaline minerals, such as limestone, tend to be more hydrophobic. It has been observed that the mineral aggregates appear to have a greater attraction for water than for oil or bitumens and that it is difficult to obtain complete or satisfactory coating of aggregates by oil or bitumen when water is present. Furthermore, even though satisfactory coating may be obtained by using dry aggregates, the oil or bitumen tends to be displaced if water enters the pavement or road.
One approach which has been used to decrease the severity of the problems attributed to poor adhesion between the aggregate and bitumens and/or stripping of the bitumen from the aggregate due to the presence of moisture has been to include an additive (hereinafter referred to as an antistripping agent) in the bitumen prior to combination with the aggregate. These antistripping agents serve to enhance the coating of the aggregate by bitumens and retard displacement of the aggregate-bitumen bond by water.
The art discloses several antistripping agents which are useful as additives in bitumens and asphalts. For example, U.S. Pat. No. 2,759,839 to Crews et al. discloses antistripping agents having the formula: ##STR1## where R is an alkyl group of at least about 8 carbon atoms, R' is an ethylene or propylene radical, and x and y are integers, the sum of which is not greater than about 8.
U.S. Pat. No. 3,615,797 discloses bitumen additives which improve the adhesion properties of the bitumen. These additives have the formula: ##STR2## wherein R is an alkyl or alkenyl radical of 8 to 22 carbon atoms; a, b, c and d are integers from 1 to 7 and the sum of a+b+c+d is from 4 to 10; A is an organic or inorganic acid and m is 0 or an integer from 1 to 3, its acid salts and mixtures thereof.
Organic compounds which are structurally similar to those disclosed in U.S. Pat. Nos. 2,759,839 and 3,615,797 but which have utilities other than as antistripping additives for bitumens and asphalts are disclosed in the following patents:
U.S. Pat. No. 2,767,214 to Bersworth discloses polyhydroxy polyalkylene polyamines which are useful as surface active agents, detergents, wetting agents and as intermediates in the production of soap-like amino compounds. The polyhydroxy polyalkylene polyamines have the general structural formula: ##STR3## wherein Y is a bivalent alkylene chain containing from 2 to 3 carbon atoms; X is a bivalent alkylene radical of from 4 to 12 carbon atoms which may be interrupted with ether oxygen atoms; Z is a bivalent alkylene radical of from 2 to 6 carbon atoms which may be either branched or straight chained; and A is a member of the group consisting of hydrogen and one of the substituent groups consisting of methyl, ethyl, n-propyl, isopropyl and butyl.
U.S. Pat. No. 2,901,461 to Auerbach et al. discloses hydroxyalkyl alkylene polyamines containing at least one hydroxyalkyl group and at least three amino hydrogen atoms per molecule which are useful as hardeners for polyepoxy compounds and which have the general formula: ##STR4## wherein x is an integer from zero to 3, n is an integer from 2 to 6, R in each instance is a monovalent substituent being either hydrogen or a hydroxyalkyl group, and the number of instances per molecule where R represents a hydroxyalkyl group being at least one, but less than x+2.
U.S. Pat. No. 3,200,155 discloses compounds having the formula: ##STR5## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are selected from the group consisting of hydrogen, HOCH.sub.2 CH.sub.2 --, ##STR6## wherein R.sub.6 is one of hydrogen, methyl or ethyl in at least one occurrence and another one of hydrogen, methyl and ethyl in the remainder of occurrences, x is a small integer, and at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 is one of the aforedefined groups other than hydrogen. The disclosed compounds are useful as chemical intermediates and cross-linking agents.